Means for adjusting stop aperture of cameras relatively to distance



Jan. 13, 1931. J. G; BEACH 1,788,655

- MEANS FORADJUSTING STOP APERTURE OF CAMERASRELATIVELY 'I'O DISTANCEFiled Aug. 6, 1927 SMALL ovsuma LARGE OPENINO Bn hl'unabine Fair 7 Innzen 7 Patented Jan. 1 1931' PATENT "mm;

urine enonen amen, or ron'rnm, onn qon ron anw's'rnae s'ror arnnrunn orcmnas RELATIVELY 'ro nrs'rmcn Application m au ust 6, 19271. semi swi aMy inventi'onrelates particularly tophotographic' cameras now generally,usedfor instantaneous exposures. j V

The object of my invention is to provide a a simpleand definite methodand means for determinin the proper size of the stop aperture of the ensto be used when photographinglobjec'ts, in order to obtain a goodpicture i n preserve a uniformity of exposure for -10' all subjectsunder the same lighting" conditions. I

It is known that there is a'relation between the'distance of the objectto be photographed 1 from the camera lens, and the required size 15ofstop aperture, and means havebeen pro- "vided for adjusting the sizeof the stop aperture a'utomaticallywith the movementof the lens frame inadjusting the focal range. But since the focal range has only a shortrange, for example, a hundred feet, w en' the object is locateda eaterdistance away, this adjustment woul require a variable exposure range.It was assumed that this relation was more or less dependent upon thesubject "to be" photographed, and the exposure.

Therefore it has heretofore been the custom p todetermine thesiz'e ofthestop a erture by referring to a published groupyo subjects each groupbeing marked with a recommend-a aperture to beused in taking apher thenselecting edsize ofsto the picture; t e photogr the group in which hisparticularsubject be longs, and using the stop aperture'reoommended. a

I have discovered that adefinite relation exists between the size ofstop aperture re.- quired to be used and the distance from the cameralens to the'obj ect to bephotographed andithat this co-relation is;independent of the focus of thelens, and exists for any lens,

' and for any speed of lens.

Thus,- for a lens of given speed the size of the stop aperture should bereduced proper tionallyto the distance of the object from V the lens,andthis distance should beapproxiapher, with reference to a scaleprovided orxthat mately determined the photo purpose on the camera andthe roper stop op'eningobtained automatically y roperly' .9 positioningan indicator of said sea 0.

ries of lineal scales, one to be used in place of To this end myinvention consists in providing in a camera, in combination with a stopadjustable to vary theopening thereof, a llneal scale representing thevanable dis tance from the camera lens to the object to be photographed,indicator movable over said scale and an operating connection from suchpointer to the adjusting element of the; said stop, whereby inpositioning the indicat-' or tothe'approximate distance of the objectfrom thev lens, the greater the distance the smaller proportionatelywill be the openin of said stop, substantiall as described. preferablythe lineal sca e is made up of a sethe. other in positioning theindicator of the scale under certain lig ting conditions. By this modeand means of determining the size a of the stopaper'ture the taking ofplctures is reatly simplified becausethe adjustment of t e stop aperturebecomes definite; thuseliminatinguncertainty in photogra by, and alsoeliminating the tedious task of aving to de-' termine the adjustment ofthe stop aperture with reference to instructions covering the 76-particular group of subjects. In short, m I inventionpermitsall icturesto bemade wit the same ex osure, or exam le with good lighting conitions,.a'snap s ot -'no matter what distance the subject is from thelens, and no matter what the subject, provided the otherexposure-influencing conditions are uniform. I

p In the accompanfiying drawings, forming a part of this'speci cation,Fig. 1 re resents diagrammaticallythe front view o a cam-. era. t

Fig.2 and Fig. 3 are fragmentary views of the lens frame of the camera.showing particularly that part which holds'the stop and showin theaperture arranged for two dif ferent istan'ces and the means to. adjustit in accordance with m invention. I

Fig. 4 is a rap illustrating the required adjustment 0 the stop-aperturerelatively to and i Fig. 5 represents the scale element as consistinglof aseries of registering scales, one or the t er of whicheis't0 used inpo'sitioning 190 95 given distances of the object'from thelens;

the indicator in order to allow for variations in lighting conditions.

The ty of camera shown represents the Premo. gince my invention dea sonly with the stop, and the adjustment of its aperture, those parts willbe alone described in detail, and the other details will be assumed tobe constructed as usual.

Thus, the camera a is provided with a con- For a distance of 6 feet,

For a distance of 8 feet For a distance of feet, For a distance of 100feet,

For a distance of 500 feet For a distance of 8 feet For a distance of 25feet For a distance of 100 feet For a distance of 500 feet lens of thecamera.

It is suflicient that the points indicatin arbitrary distances. The armf is provided with a pointer or indicator f, which'works over the scaleg.

I have discovered that the size of the aperture of the lens stop must bereduced in correspondence with the increase ofthe distance scalerepresent between the object and thelens in the following proportions 4For example using a f3.5 lens and having a full open stop for an object6 feet away from the lens, then ,the stop sizes would be as follows:

For a distance of For a distance of For a. distance of For a distance of6 feet, the stop would be 8 feet, the stop wouldbe 25 feet, the stopwould be 100 feet, the stop would be For a distanceof 500 feet, the stopwould be For a distance of 3000 feet, the stop would be For a distanceof 20000 feet, the stop would be and for other distances the percentageswould be intermediate the amounts given.

A second example using a f4.5 lens and havin a full open stop foranobject 6 feet away from the lens, then the stop sizes would be asfollows:

For a distance of For a distance of 8 feet, the stop would be For adistance of I 25 feet, the step would be For a distance of 100 feet, thestop would be For a distance of 500 feet, the stop would be For adistance of 3000 feet, the stop would be For other distances thepercentages would be intermediate and for snap shot work the stop sizeof 20% of the full diameter would remain the same size for all distancesover 3000 feet.

A third example using a f 6.3 lens and having the full open stop for anobject 6 feet away from the lens, then the stop sizes would be asfollows:

the stop would be 100% of its full diameter ,the stop would be 78%% ofits full diameter 31w stop wouig 1be 01f illg diameger esopwou e oo is uciameer the stop would be 27 of its full diameter For other distancesthe percentages would be intermediate, and for snap shot work the stopsize of 27 of the full diameter would remain the same size for alldistances over 500 feet.

A fourth example usin a #80 lens and having the full open stop for anobject 8 feet away from the lens, then the stop sizes would be asfollows:

,the stop would be 100% of its full diameter the stop would be 91) ofits full diameter the stop would be 50% of its full diameter the stopwould be 35 of its full diameter For other distances the percentageswould be intermediate the amounts given and for snap shot work the stopsize of 35 of the full diameter would remain the same size for alldistances over 500 feet.

These percentages give sufiicient data for the marking of distancescales for the 4 lenses in common use. The distances to the object whichcorrespond to sizes of apertures as here indicated, or as applicable toother lenses, or to other adjustments of stop sizes to distances as maybe taken to meet any required exposure, may be varied and yet retain auniformity of exposure for all pic- 100% I of its full diameter 87 ofits full diameter 62%% of its full diameter 43 of its full diameter 31%%of its full diameter 21 of its full diameter 15 of its full diametertures and still have an which would yield a good print, this allowablevariation being due to the latitude of exposure allowable when using thepresent day plates or films.

The stop adjustments above given are to be effective exposure 6 feet,the stop would be 100% of its full diameter 80% of its full diameter 56%of its full diameter 40% of its full diameter 28% of its full diameter20% of its full diameter means understood as those to be used under goodlighting conditions, for example bri ht sunlight, but under poorlighting condit1ons, for example dull days, the stop aperture could bemoved to the next larger size, thus avoiding the making of a longerexposure.

The foregoing adjustments of the stop apertures relatively to the givendistances is graphically represented by Fig. 4 of the drawing.

A multiple scale 9' could be employed, as illustrated by Fig. 5, alsosuch scale may be composed of three concentric elements 7', k, Z overwhich the arm m is operated to adjust the stop aperture 1', as todistance, but at the same time with reference to prevailing lightingconditions. By means of this scale a constant exposure could be used forany subject at any distance and for any intensity of lighting; this byhaving the different distances necessary recorded thereon and soarranged that when the stop indicator (which has recorded upon it thedifferent intensities of lighting being used) is moved to the distancemark upon the scale which is opposite the intensity of the lightingbeing used, the stop to give a constant exposure will be automaticallyset; this constant exposure under all conditions being a necessity formovie or cinema cameras and could also be used to great advantage uponthe regular instantaneous type of camera.

To operate the camera when equipped with this means of stop sizeadjustment, place the stop adjuster f of Fig. '1, at point showingdistance to the object. This will give the correct stop to use forthepicture.

A few examples are here given to illustrate the simplicity of exposuremanipulations upon the camera and to show the resulting uniform systemof exposure, when using,

a for example, a 'f,3.5 lens, films, and considering the subjects asaverage in color tone,

ing this means of stop size regulation.

. A portrait, distance 6 feet. Set the camera focus at 6 feet. Set thestop indicator f at 6 feet.

'- The exposure will be 1/100 second.

- Set the camera focus at 50 feet.

A street scene, principal object 50 feet away.

Set the stop indicator f at 50 feet. The exposure will be 1/100 second.

adjustable to vary the size of the opening thereof, a lineal scalerepresenting the variable distance from the camera lens to the ob jectto be hotographed and extended and graduated or distances beyond theinfinity focus position of the lens, an indicator movable independentlyof the focusing mechanism, over said scale and an operating connectionfrom such pointer to the adjusting element of the said stop, whereby inpositioning the indicator to the approximate distance of the objectfromthe lens, the greater the distance the smaller proportionately willbe the opening of said stop,'substantially as described.

2. In a camera in combination with a stop adjustable to vary the size ofthe opening thereof, a series of re istering lineal scales representingthe varia le distance from the camera lens to the object to be(photographed,

an indicator movable over sai scales and an operating connection fromsuch pointer to the adjusting element of the said stop, whereby v inpositioning the indicator to the approxilighting a midday summersunshine and usi

